Federal Agencies’ Use of the Social Costs of Greenhouse Gases in NEPA Analysis

The social cost of greenhouse gas estimates are useful for quantifying climate impacts in analyses conducted under the National Environmental Policy Act (NEPA). Although the Interagency Working Group (IWG) social costs of greenhouse gases metrics were originally developed for use by federal agencies in rulemakings, the metrics are applicable for project-level determinations under NEPA, and have been used in some evaluations of projects and plans. 

Currently, though some agencies have used the social costs of greenhouse gases in NEPA analysis, no agency regularly uses the metric in environmenta impact statements or envirornmental assessments, but this may change as a result of recent guidance. 1  A number of other agencies, however, have never used the tool despite evaluating projects with major greenhouse gas effects. Below are examples of when agencies have or should have applied the social cost metrics in NEPA analysis to assess a project’s climate impacts.

This page was last updated on April 5, 2021. Please contact [email protected] with any questions.

Regularly Use

Lead Agency Examples
None None

Occasionally Use 2

Lead Agency Examples
US Forest Service, Department of Agriculture

Used

Did Not Use

US Army Corps of Engineers

Used

Did Not Use

United States Postal Service

Used

Next Generation Delivery Vehicle Acquisitions (Draft, 2021)

U.S. Department of the Interior, Office of Surface Mining

Used

Did Not Use

U.S. Department of the Interior, Bureau of Land Management

Used

Did Not Use

National Highway Traffic Safety Administration

Used

Bureau of Reclamation

Used

Bureau of Ocean Energy Management

Used

Never Use 3

Lead Agency Examples
United States Nuclear Regulatory Commission
Federal Highway Administration
Federal Energy Regulatory Commission, Department of Energy
  1. To date, no agencies default to using the Interagency Working Group (IWG) social costs of greenhouse gases metric in NEPA analysis documents with significant greenhouse gas emissions effects (~ 1,000,000 metric tons of carbon dioxide annually); however, this will likely change as a result of recent guidance issued by the Biden Administration. See Exec. Order 13,990, 86 Fed. Reg. 7037 (Jan. 25, 2021).  ↩︎
  2. These examples compile NEPA analyses (environmental impact statements or environmental assessments) in which an agency used the IWG social costs of greenhouse gases to assess a project’s climate impacts. ↩︎
  3. These examples compile NEPA analyses (environmental impact statements or environmental assessments) for projects with significant greenhouse gas emissions, see note 1, in which agencies did not use the social cost metrics or rejected their suitability for assessing a project’s climate impacts. ↩︎